Piedmont proves liquid enzyme catalysis works at commercial scale

By Ron Kotrba | February 07, 2012

The founder of Pittsboro, N.C.-based Piedmont Biofuels, Rachel Burton, gave details at the 2012 National Biodiesel Conference & Expo in Orlando on the company’s new commercially proven enzymatic transesterification process.

Last year at this time, Burton introduced Piedmont Biofuels’ FAeSTER process, an enzymatic pretreatment developed in collaboration with global enzyme maker Novozymes, to replace acid esterification.

The FAeSTER process used immobilized enzymes, or enzymes fixed to a medium, to esterify free fatty acids (FFAs) into biodiesel.

Now, supported by a U.S. DOE Small Business Innovation and Research grant, in addition to the technology commercialization support from the Clean Energy Alliance under the DOE Small Business and Clean Energy Alliance Partnership, the innovative team at Piedmont Biofuels has “switched gears,” as she said, and developed the first commercial-scale transesterification process using liquid, rather than immobilized, enzymes.

The FAeSTER process still has its uses in Piedmont Biofuels’ new approach, but instead of using it as a pretreatment step, it is now utilized as a fuel polishing procedure to convert FFAs in the biodiesel on the backend of the production cycle. Also, the feedstock can contain water with no issues, unlike when using chemical catalysts, which would cause soaps to form and loss of product yield.

During the same panel, Novozymes’ P.M. Nielsen discussed the same approach, but instead of using enzymatic polishing, the company’s patent-pending BioFAME process uses a caustic wash to clean the fuel.

The liquid enzymes can be reused up to 10 times with 90 to 95 percent conversion rate. “The breakeven point is five or six uses,” Burton said. The liquid enzymes in the water/glycerin phase can be re-circulated back to the reactor, or they can be recovered through membrane filtration.

The resulting glycerin is 97 percent pure, giving added value to the coproduct.

Another benefit, Burton said, is that the processing can be done at relatively low temperatures, between 35 and 40 degrees Centigrade.

Burton said just a couple of weeks ago Piedmont Biofuels scaled up to commercial volumes, 2,700 gallons in a coil-heated cone-bottom reactor. The feedstock was soy oil. After only six to eight hours of residence time, she said the results were “amazing”—less than 2 percent FFAs and the reaction went to completion.

This, Burton emphasized, proves that a 100 percent enzyme-converted fuel can meet ASTM quality specifications. 


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